No, the number of stacks and the rank in the skill both influence the slag chance
…
There are plenty of good things about IO. Sure you could be doing the same amount of damage by shooting instead of waiting for your stacks to fill up, but the reverse is also true: You don’t have to shoot and you are still “doing damage”. It’s a skill that stabilizes your DPS by filling up any gaps with potential damage.
Any time you’re moving from one area to the next, you’re still “doing damage”
Any time you’re reloading, ducking behind cover, throwing a grenade, summoning DT, switching gun… you’re still doing damage. It encourages you to take other actions without losing your DPS. that in itself is very very good.
And on top of that, it debuffs!
The first shot of any engagement is almost always a guaranteed slagged target…with a big missing chunk of health.


